Steps to repro:

1. Open Unity;
2. Create new project;
3. Import attached 'NormalMapTerrainBug' unitypackage;
4. Open 'test' scene;

5. Notice that in the scene there is terrain with initial 2d texture, containing normal map;
6. Scroll out in the Scene view.

7. Notice that at some point normal map disappears from terrain (see attached gif video and actual.png screenshot).
8. In the Paint texture tab of Terrain component choose initial texture;
9. Click on terrain (viewpoint should still be far from terrain;

10. Notice that normap appears when clicking on terrain with selected initial texture in the paint texture tool (see attached gif video). This brings inconsistency within product, since normal map texture appears only when clicking on terrain when viewpoint is far from it.

Expected result:
Normal map texture should not disappear when moving viewpoint far from terrain; it should also be consistent with paint texture tool.

Notes:
- Reproducible in: 5.4.0b10, 5.4.0b9, 5.3.3p3, 5.3.2f1, 5.3.1f1, 5.2.2.f4;
- Reproducible on both Windows 10 and OSX 10.11;
- Not reproducible in Game view.